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Cost of Paint Thinner vs. Mineral Spirits
Usually, paint thinner is cheaper to purchase, and by a pretty good amount. The difference between the two can be up to 100%, or double the cost for mineral spirits. The reason for this is that the mineral spirits receives additional, more thorough refinement, which takes more manpower. This cleaning of the material also is what makes it less noxious to use. The bottom line is that it takes more work to produce mineral spirits than paint thinner, and just as there is a price difference in an oil change and a cooling system flush, so there will be a difference in these 2 products.
Effectiveness of Paint Thinner vs. Mineral Spirits
Many people have developed preferences on the use of mineral spirits or paint thinner. Many prefer one over the other. However, the observant user will find that the mineral spirits tend to be more effective in terms of solvent properties and cleaning capabilities. This is most likely due to the fact that it is a much more purified form than paint thinner is. Many artists prefer mineral spirits due to the substance's ability to quickly clean about any painting utensil that might be used. It is also a more effective solvent, and is the preferable thinning fluid. One argument is that because it is more effective overall when used in this way, that it makes up for the difference in cost compared to paint thinner.